Method and apparatus for an improved bellows shield in a plasma processing system

ABSTRACT

The present invention presents an improved bellows shield for a plasma processing system, wherein the design and fabrication of the bellows shield coupled to a substrate holder electrode advantageously provides protection of a bellows with substantially minimal erosion of the bellows shield.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. Ser. No. 10/259,306, filed Sep. 30, 2002.This application also is related to U.S. Pat. No. 7,147,749, entitled“Method and apparatus for an improved upper electrode plate withdeposition shield in a plasma processing system”, issued Dec. 12, 2006;U.S. Pat. No. 6,837,966, entitled “Method and apparatus for an improvedbaffle plate in a plasma processing system”, issued Jan. 4, 2005; U.S.Pat. No. 7,166,166, entitled “Method and apparatus for an improvedbaffle plate in a plasma processing system”, issued on Jan. 23, 2007;U.S. Pat. No. 7,137,353, entitled “Method and apparatus for an improveddeposition shield in a plasma processing system”, issued on Nov. 21,2006; U.S. Pat. No. 6,798,519, entitled “Method and apparatus for animproved optical window deposition shield in a plasma processingsystem”, issued on Sep. 28, 2004; and U.S. Pat. No. 7,166,200, entitled“Method and apparatus for an improved upper electrode plate in a plasmaprocessing system”, issued on Jan. 23, 2007. The entire contents of allof those applications are herein incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to an improved component for a plasmaprocessing system and, more particularly, to a bellows shield employedin a plasma processing system to protect a bellows.

BACKGROUND OF THE INVENTION

The fabrication of integrated circuits (IC) in the semiconductorindustry typically employs plasma to create and assist surface chemistrywithin a plasma reactor necessary to remove material from and depositmaterial to a substrate. In general, plasma is formed within the plasmareactor under vacuum conditions by heating electrons to energiessufficient to sustain ionizing collisions with a supplied process gas.Moreover, the heated electrons can have energy sufficient to sustaindissociative collisions and, therefore, a specific set of gases underpredetermined conditions (e.g., chamber pressure, gas flow rate, etc.)are chosen to produce a population of charged species and chemicallyreactive species suitable to the particular process being performedwithin the chamber (e.g., etching processes where materials are removedfrom the substrate or deposition processes where materials are added tothe substrate).

Although the formation of a population of charged species (ions, etc.)and chemically reactive species is necessary for performing the functionof the plasma processing system (i.e. material etch, materialdeposition, etc.) at the substrate surface, other component surfaces onthe interior of the processing chamber are exposed to the physically andchemically active plasma and, in time, can erode. The erosion of exposedcomponents in the plasma processing system can lead to a gradualdegradation of the plasma processing performance and ultimately tocomplete failure of the system.

In order to minimize the damage sustained by exposure to the processingplasma, components of the plasma processing system, known to sustainexposure to the processing plasma, are coated with a protective barrier.For example, components fabricated from aluminum can be anodized toproduce a surface layer of aluminum oxide, which is more resistant tothe plasma. In another example, a consumable or replaceable component,such as one fabricated from silicon, quartz, alumina, carbon, or siliconcarbide, can be inserted within the processing chamber to protect thesurfaces of more valuable components that would impose greater costsduring frequent replacement. Furthermore, it is desirable to selectsurface materials that minimize the introduction of unwantedcontaminants, impurities, etc. to the processing plasma and possibly tothe devices formed on the substrate.

In both cases, the inevitable failure of the protective coating, eitherdue to the integrity of the protective barrier or the integrity of thefabrication of the protective barrier, and the consumable nature of thereplaceable components demands frequent maintenance of the plasmaprocessing system. This frequent maintenance can produce costsassociated with plasma processing down-time and new plasma processingchamber components, which can be excessive.

SUMMARY OF THE INVENTION

The present invention provides an improved bellows shield for a plasmaprocessing system, wherein the design and fabrication of the bellowsshield advantageously addresses the above-identified shortcomings.

It is an object of the present invention to provide a bellows shieldthat can be coupled to a substrate holder of the plasma processingsystem. The plasma processing system comprises a cylindrical wall havingan inner surface, an outer surface, a first end, and a second end. Thefirst end of the cylindrical wall can comprise an attachment flange,wherein the attachment flange comprises an interior surface coupled tothe inner surface of the cylindrical wall and configured to mate withthe substrate holder, an inner radial surface, and an exterior surfacecoupled to the outer surface of the cylindrical wall. The second end ofthe cylindrical wall can comprise an end surface.

The attachment flange of the bellows shield can further include aplurality of fastening receptors for receiving fastening devices inorder to attach the bellows shield to the substrate holder. Eachfastening receptor can comprise an entrant cavity, an exit through-hole,and an inner receptor surface.

The bellows shield can further comprise a protective barrier formed on aplurality of exposed surfaces of the bellows shield facing theprocessing plasma.

It is a further object of the present invention that the plurality ofexposed surfaces of the bellows shield comprises the end surface of thecylindrical wall, the outer surface of the cylindrical wall, and theexterior surface of the attachment flange contiguous with the outersurface of the cylindrical wall.

The present invention provides a method of producing a bellows shield inthe plasma processing system comprising the steps: fabricating thebellows shield; anodizing the bellows shield to form a surfaceanodization layer on the bellows shield; machining the exposed surfaceson the bellows shield to remove the surface anodization layer; andforming a protective barrier on the exposed surfaces.

The present invention may optionally include machining of other partsnot actually exposed to the plasma. Such parts may be machined in orderto provide a contact free from the anodization layer (e.g., in order toprovide a better mechanical or electrical contact). Such parts mayinclude, but are not limited to, an interior surface of the attachmentflange and an inner receptor surface of the plurality of fasteningreceptors.

The present invention provides another method of producing the bellowsshield in the plasma processing system comprising the steps: fabricatingthe bellows shield; masking the exposed surfaces on the bellows shieldto prevent formation of a surface anodization layer; anodizing thebellows shield to form the surface anodization layer on the bellowsshield; and forming a protective barrier on the exposed surfaces.

The present invention may optionally include masking of other parts notactually exposed to the plasma. Such parts may be masked in order toprovide a contact free from the anodization layer (e.g., in order toprovide a better mechanical or electrical contact). Such parts mayinclude, but are not limited to, an interior surface of the attachmentflange and an inner receptor surface of the plurality of fasteningreceptors.

The present invention also provides a combined method of machining andmasking to provide bare exposed surfaces on which to form the protectivebarrier.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages of the invention will become more apparentand more readily appreciated from the following detailed description ofthe exemplary embodiments of the invention taken in conjunction with theaccompanying drawings, where:

FIG. 1 shows a simplified block diagram of a plasma processing systemcomprising a bellows shield according to an embodiment of the presentinvention;

FIG. 2 shows a cross-sectional view of a bellows shield for a plasmaprocessing system according to an embodiment of the present invention;

FIG. 3 shows a partial plan view of a bellows shield for the plasmaprocessing system according to an embodiment of the present invention;

FIG. 4 shows an exploded view of an attachment flange of the bellowsshield for the plasma processing system according to an embodiment ofthe present invention;

FIG. 5 shows an exploded view of an end surface on a second end of thebellows shield for the plasma processing system according to anembodiment of the present invention;

FIG. 6 presents a method of producing a bellows shield for the plasmaprocessing system according to an embodiment of the present invention;

FIG. 7 presents a method of producing a bellows shield for the plasmaprocessing system according to another embodiment of the presentinvention; and

FIG. 8 presents a method of producing a bellows shield for the plasmaprocessing system according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF AN EMBODIMENT

According to an embodiment of the present invention, a plasma processingsystem 1 is depicted in FIG. 1 comprising a plasma processing chamber10, an upper assembly 20, an electrode plate 24, a substrate holder 30for supporting a substrate 35, and a pumping duct 40 coupled to a vacuumpump (not shown) for providing a reduced pressure atmosphere 11 inplasma processing chamber 10. Plasma processing chamber 10 canfacilitate the formation of a processing plasma in a process space 12adjacent substrate 35. The plasma processing system 1 can be configuredto process substrates of various sizes (e.g., 200 mm substrates, 300 mmsubstrates, or larger).

In the illustrated embodiment, upper assembly 20 can comprise at leastone of a cover, a gas injection assembly, and an upper electrodeimpedance match network. For example, the electrode plate 24 can becoupled to an RF source. In another alternate embodiment, the upperassembly 20 comprises a cover and an electrode plate 24, wherein theelectrode plate 24 is maintained at an electrical potential equivalentto that of the plasma processing chamber 10. For example, the plasmaprocessing chamber 10, the upper assembly 20, and the electrode plate 24can be electrically connected to ground potential.

Plasma processing chamber 10 can, for example, further comprise adeposition shield 14 for protecting the plasma processing chamber 10from the processing plasma in the process space 12, and an opticalviewport 16. Optical viewport 16 can comprise an optical window 17coupled to the backside of an optical window deposition shield 18, andan optical window flange 19 can be configured to couple optical window17 to the optical window deposition shield 18. Sealing members, such asO-rings, can be provided between the optical window flange 19 and theoptical window 17, between the optical window 17 and the optical windowdeposition shield 18, and between the optical window deposition shield18 and the plasma processing chamber 10. Optical viewport 16 can, forexample, permit monitoring of optical emission from the processingplasma in process space 12.

Substrate holder 30 can, for example, further comprise a verticaltranslational device 50 surrounded by a bellows 52 coupled to thesubstrate holder 30 and the plasma processing chamber 10, and configuredto seal the vertical translational device 50 from the reduced pressureatmosphere 11 in plasma processing chamber 10. Additionally, a bellowsshield 54 can, for example, be coupled to the substrate holder 30 andconfigured to protect the bellows 52 from the processing plasma.Substrate holder 10 can, for example, further be coupled to at least oneof a focus ring 60, and a shield ring 62. Furthermore, a baffle plate 64can extend about a periphery of the substrate holder 30.

Substrate 35 can be, for example, transferred into and out of plasmaprocessing chamber 10 through a slot valve (not shown) and chamberfeed-through (not shown) via robotic substrate transfer system where itis received by substrate lift pins (not shown) housed within substrateholder 30 and mechanically translated by devices housed therein. Oncesubstrate 35 is received from substrate transfer system, it is loweredto an upper surface of substrate holder 30.

Substrate 35 can be, for example, affixed to the substrate holder 30 viaan electrostatic clamping system. Furthermore, substrate holder 30 can,for example, further include a cooling system including a re-circulatingcoolant flow that receives heat from substrate holder 30 and transfersheat to a heat exchanger system (not shown), or when heating, transfersheat from the heat exchanger system. Moreover, gas can, for example, bedelivered to the back-side of substrate 35 via a backside gas system toimprove the gas-gap thermal conductance between substrate 35 andsubstrate holder 30. Such a system can be utilized when temperaturecontrol of the substrate is required at elevated or reducedtemperatures. In other embodiments, heating elements, such as resistiveheating elements, or thermoelectric heaters/coolers can be included.

In the illustrated embodiment, shown in FIG. 1, substrate holder 30 cancomprise an electrode through which RF power is coupled to theprocessing plasma in process space 12. For example, substrate holder 30can be electrically biased at a RF voltage via the transmission of RFpower from a RF generator (not shown) through an impedance match network(not shown) to substrate holder 30. The RF bias can serve to heatelectrons to form and maintain plasma. In this configuration, the systemcan operate as a reactive ion etch (RIE) reactor, wherein the chamberand upper gas injection electrode serve as ground surfaces. A typicalfrequency for the RF bias can range from 1 MHz to 100 MHz and ispreferably 13.56 MHz. RF systems for plasma processing are well known tothose skilled in the art.

Alternately, the processing plasma formed in process space 12 can beformed using a parallel-plate, capacitively coupled plasma (CCP) source,an inductively coupled plasma (ICP) source, any combination thereof, andwith and without DC magnet systems. Alternately, the processing plasmain process space 12 can be formed using electron cyclotron resonance(ECR). In yet another embodiment, the processing plasma in process space12 is formed from the launching of a Helicon wave. In yet anotherembodiment, the processing plasma in process space 12 is formed from apropagating surface wave.

Referring now to an illustrated embodiment of the present inventiondepicted in FIG. 2 (cross-sectional view) and FIG. 3 (partial planview), bellows shield 54 comprises a cylindrical wall 80, thecylindrical wall 80 comprising an inner surface 82, an outer surface 84,a first end 86, and a second end 88. The first end 86 of cylindricalwall 80 comprises an attachment flange 90 coupled to the cylindricalwall 80 and configured to attach the bellows shield 54 to the substrateholder 30, and a through-hole 92 to accommodate an upper surface of thesubstrate holder 30. The second end 88 of the cylindrical wall 80comprises an end surface 94.

FIG. 4 provides an expanded view of the attachment flange 90 coupled tocylindrical wall 80 and configured to couple the bellows shield 54 tothe substrate holder 30. The attachment flange 90 comprises an interiorsurface 96, an inner radial surface 97, and an exterior surface 98.Additionally, the interior surface 96 can comprise a mating surface 99and the exterior surface can comprise a mounting surface 91 that areconfigured to couple the bellows shield 54 to the substrate holder 30.

Furthermore, attachment flange 90 can, for example, comprise a pluralityof fastening receptors 100, each fastening receptor 100 coupled to theinterior surface 96 and the exterior surface 98, and configured toreceive fastening devices (not shown) (such as bolts) to couple bellowsshield 54 to substrate holder 30. The fastening receptors 100 cancomprise an entrant cavity 102, an exit through-hole 104, and an innerreceptor surface 106. For example, the number of fastening receptors 100formed within bellows shield 54 can range from 0 to 100. Desirably, thenumber of fastening receptors 100 can range from 5 to 20; and,preferably, the number of fastening receptors 100 is at least 6.

FIG. 5 provides an expanded view of the end surface 94 forming thesecond end 88 of the cylindrical wall 80.

Referring now to FIGS. 2 through 5, the bellows shield 54 furthercomprises a protective barrier 150 formed on a plurality of exposedsurfaces 110 of the bellows shield 54. In an embodiment of the presentinvention, the plurality of exposed surfaces 110 can comprise the endsurface 94 of the cylindrical wall 80, the outer surface 84 of thecylindrical wall 80, and the exterior surface 98 of the attachmentflange 90 contiguous with the outer surface 84 of the cylindrical wall80. Alternately, the exposed surfaces 110 can further comprise all ofthe surfaces remaining on the bellows shield 54.

In an embodiment of the present invention, the protective barrier 150can comprise a compound including an oxide of aluminum such as Al₂O₃. Inanother embodiment of the present invention, the protective barrier 150can comprise a mixture of Al₂O₃ and Y₂O₃. In another embodiment of thepresent invention, the protective barrier 150 can comprise at least oneof a III-column element (column III of periodic table) and a Lanthanonelement. In another embodiment of the present invention, the III-columnelement can comprise at least one of Yttrium, Scandium, and Lanthanum.In another embodiment of the present invention, the Lanthanon elementcan comprise at least one of Cerium, Dysprosium, and Europium. Inanother embodiment of the present invention, the compound formingprotective barrier 150 can comprise at least one of Yttria (Y₂O₃),Sc₂O₃, Sc₂F₃, YF₃, La₂O₃, CeO₂, Eu₂O₃, and Dy₂O₃.

In an embodiment of the present invention, the protective barrier 150formed on bellows shield 54 comprises a minimum thickness, wherein theminimum thickness can be specified as constant across at least one ofthe plurality of exposed surfaces 110. In another embodiment, theminimum thickness can be variable across at least one of the pluralityof exposed surfaces 110. Alternately, the minimum thickness can beconstant over a first portion of at least one of the plurality ofexposed surfaces 110 and variable over a second portion of at least oneof the plurality of exposed surfaces 110 (i.e., a variable thickness canoccur on a curved surface, on a corner, or in a hole). For example, theminimum thickness can range from 0.5 micron to 500 micron. Desirably,the minimum thickness ranges from 100 micron to 200 micron; and,preferably, the minimum thickness is at least 20 micron.

FIG. 6 presents a method of producing the bellows shield in the plasmaprocessing system described in FIG. 1 according to an embodiment of thepresent invention. A flow diagram 300 begins in 310 with fabricating thebellows shield 54 (as described above). Fabricating the bellows shieldcan comprise at least one of machining, casting, polishing, forging, andgrinding. For example, each of the elements described above can bemachined according to specifications set forth on a mechanical drawing,using conventional techniques including a mill, a lathe, etc. Thetechniques for machining a component using, for example, a mill or alathe, are well known to those skilled in the art of machining. Thebellows shield 54 can, for example, be fabricated from aluminum.

In 320, the bellows shield is anodized to form a surface anodizationlayer. For example, when fabricating the bellows shield from aluminum,the surface anodization layer comprises aluminum oxide (Al₂O₃). Methodsof anodizing aluminum components are well known to those skilled in theart of surface anodization.

In 330, the surface anodization layer is removed from the exposedsurfaces 110 using standard machining techniques. In this step, or in aseparate step, additional non-exposed surfaces (e.g., a mating surfaceof an interior surface of the attachment flange and an inner receptorsurface of the plurality of fastening receptors) may also be machined.Such non-exposed surfaces may be machined in order to provide bettermechanical or electrical contacts between those parts and the parts withwhich they are mated.

In 340, the protective barrier 150 is formed on the exposed surfaces110. A protective barrier comprising, for example Yttria, can be formedusing (thermal) spray coating techniques that are well known to thoseskilled in the art of ceramic spray coatings. In an alternateembodiment, forming the protective barrier can further comprisepolishing (or smoothing) the thermal spray coating. For example,polishing the thermal spray coating can comprise the application of sandpaper to the sprayed surfaces.

FIG. 7 presents a method of producing the bellows shield in the plasmaprocessing system described in FIG. 1 according to another embodiment ofthe present invention. A flow diagram 400 begins in 410 with fabricatingthe bellows shield 54 (as described above). Fabricating the bellowsshield can comprise at least one of machining, casting, polishing,forging, and grinding. For example, each of the elements described abovecan be machined according to specifications set forth on a mechanicaldrawing, using conventional techniques including a mill, a lathe, etc.The techniques for machining a component using, for example, a mill or alathe, are well known to those skilled in the art of machining. Thebellows shield 54 can, for example, be fabricated from aluminum.

in 420, the exposed surfaces 110 are masked to prevent the formation ofa surface anodization layer thereon. In this step, or in a separatestep, additional non-exposed surfaces (e.g., an interior surface of theattachment flange and an inner receptor surface of the plurality offastening receptors) may be masked. Such non-exposed surfaces may bemasked in order to provide better mechanical or electrical contactsbetween those parts and the parts with which they are mated. Techniquesfor surface masking and unmasking are well known to those skilled in theart of surface coatings and surface anodization.

In 430, the bellows shield is anodized to form a surface anodizationlayer on the remaining unmasked surfaces. For example, when fabricatingthe bellows shield from aluminum, the surface anodization layer cancomprise aluminum oxide (Al₂O₃). Methods of anodizing aluminumcomponents are well known to those skilled in the art of surfaceanodization.

In 440, the protective barrier 150 is formed on the exposed surfaces110. A protective barrier comprising, for example Yttria, can be formedusing (thermal) spray coating techniques that are well known to thoseskilled in the art of ceramic spray coatings. In an alternateembodiment, forming the protective barrier can further comprisepolishing (or smoothing) the thermal spray coating. For example,polishing the thermal spray coating can comprise the application of sandpaper to the sprayed surfaces.

FIG. 8 presents a method of producing the bellows shield in the plasmaprocessing system described in FIG. 1 according to another embodiment ofthe present invention. A flow diagram 500 begins in 510 with fabricatingthe bellows shield 54 (as described above). Fabricating the bellowsshield can comprise at least one of machining, casting, polishing,forging, and grinding. For example, each of the elements described abovecan be machined according to specifications set forth on a mechanicaldrawing, using conventional techniques including a mill, a lathe, etc.The techniques for machining a component using, for example, a mill or alathe, are well known to those skilled in the art of machining. Thebellows shield pan, for example, be fabricated from aluminum.

In 520, a protective barrier is formed on the exposed surfaces 110 ofthe bellows shield. A protective barrier comprising, for example Yttria,can be formed using (thermal) spray coating techniques that are wellknown to those skilled in the art of ceramic spray coatings. In analternate embodiment, forming the protective barrier can furthercomprise polishing (or smoothing) the thermal spray coating. Forexample, polishing the thermal spray coating can comprise theapplication of sand paper to the sprayed surfaces.

The processes of forming a protective barrier 150 on the exposedsurfaces 110, described with reference to FIGS. 6-8 can be modified toutilize a combination of machining and masking. In such a modifiedprocess, at least one exposed surface 110 is masked to prevent formationof the anodization layer thereon while other exposed surfaces 110 areanodized. The exposed surfaces 110 that are unmasked are then machined,and the exposed surfaces that were masked are unmasked. The protectivebarrier 150 can then be formed on all the exposed surfaces 110. Asdescribed above, additional surfaces that are not exposed surfaces mayalso be machined during the method (e.g., in order to provide a bettermechanical or electrical contact than we be formed with the anodizationlayer thereon.

Although only certain exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

1. A bellows shield for protecting a bellows on a substrate holder of aplasma processing system, comprising: a cylindrical wall comprising aninner surface, an outer surface, a first end, and a second end; whereinsaid first end comprises an attachment flange, said attachment flangecomprising: an interior surface having a first surface extendingradially inward from said inner surface of said cylindrical wall, and amating surface extending radially inward from said first surface andaxially recessed from said first surface, said mating surface beingconfigured to mate with said substrate holder and having a groovetherein further axially recessed from the mating surface and extendingcircumferentially around the mating surface, the groove being adjacentto the first surface an inner radial surface coupled to said matingsurface an exterior surface coupled to said outer surface and said innerradial surface, said exterior surface comprising: a first exteriorsurface extending radially inward from said outer surface of saidcylindrical wall, a second exterior surface axially protruded from saidfirst exterior surface and extending radially inward from said firstexterior surface, and a sidewall connecting said first exterior surfaceto said second exterior surface, wherein said attachment flange furthercomprises a plurality of fastening receptors coupled to said interiorsurface and said second exterior surface of said attachment flange andconfigured to receive fastening devices in order to couple said bellowsshield to said substrate holder; and wherein said second end of saidcylindrical wall comprises an end surface; and a protective barrierprovided on a plurality of exposed surfaces of said bellows shield,wherein said exposed surfaces comprise said end surface of said secondend, said outer surface of said cylindrical wall, and said exteriorsurface of said attachment flange of said first end, and said protectivebarrier is a coating which comprises yttrium or dysprosium and whereinat least a portion of said inner surface includes an anodization layerthereon and does not include said protective barrier thereon, andwherein at least a portion of said mating surface does not include ananodization layer thereon and does not include said protective barrierthereon.
 2. The bellows shield as recited in claim 1, wherein each ofsaid plurality of fastening receptors comprises an entrant cavityopening to said second exterior surface, an exit through-hole opening tosaid interior surface, and an inner receptor surface provided withinsaid fastening receptor.
 3. The bellows shield as recited in claim 2,wherein said entrant cavity comprises: a first entrant cavity opening tosaid second exterior surface; and a second entrant cavity coupling saidfirst entrant cavity to said exit through hole, wherein said secondentrant cavity is wider than said exit through hole, and said firstentrant cavity is wider than said second entrant cavity.
 4. The bellowsshield as recited in claim 3, wherein said protective barrier is notprovided on said first entrant cavity, not provided on said secondentrant cavity and not provided on said exit through-hole.
 5. Thebellows shield as recited in claim 2, wherein said protective barrier isnot provided on at least a portion said inner receptor surface.
 6. Thebellows shield as recited in claim 2, wherein said protective barrier isa spray coating and said entrant cavity comprises: a first entrantcavity opening to said second exterior surface; and a second entrantcavity coupling said first entrant cavity to said exit through hole,wherein said second entrant cavity is wider than said exit through hole,and said first entrant cavity is wider than said second entrant cavity.7. The bellows shield as recited in claim 1, wherein said bellows shieldis formed of a metal.
 8. The bellows shield as recited in claim 7,wherein said metal comprises aluminum.
 9. The bellows shield as recitedin claim 1, wherein said protective barrier is provided in directcontact with a bare surface of said bellows shield not having ananodization layer thereon.
 10. The bellows shield as recited in claim 1,wherein said protective barrier is provided only in direct contact witha bare surface of said bellows shield not having an anodization layerthereon.
 11. The bellows shield as recited in claim 1, wherein saidprotective barrier comprises a thermal spray coating having a minimumthickness and said minimum thickness is constant across at least one ofsaid exposed surfaces.
 12. The bellows shield as recited in claim 1,wherein said protective barrier comprises a thermal spray coating havinga minimum thickness and said minimum thickness is variable across atleast one of said exposed surfaces.
 13. The bellows shield as recited inclaim 1, wherein said cylindrical wall has a minimum thickness of atleast two millimeters.
 14. The bellows shield as recited in claim 1,wherein said inner radial surface comprises a minimum diameter of atleast 200 millimeters.
 15. The bellows shield as recited in claim 1wherein said outer surface of the cylindrical wall is a bare surface nothaving an anodization layer provided thereon, and said protectivebarrier is provided in direct contact with said bare surface.
 16. Thebellows shield as recited in claim 1, wherein said mating surfacecomprises a first mating surface coupled to said inner radial surface,and a second mating surface coupled to said first mating surface andsaid first surface of the interior surface, said second mating surfacebeing axially recessed from said first mating surface and said firstsurface of the interior surface to form a portion of said groove. 17.The bellows shield as recited in claim 1, wherein: said protectivebarrier is not provided on said inner surface, is not provided on saidfirst surface of the interior surface, is not provided on said secondmating surface and is not provided on said first mating surface; and ananodization layer is provided on said inner surface, said first surfaceof the interior surface and said second mating surface.
 18. The bellowsshield as recited in claim 17, wherein said first mating surface is abare metal surface not having said protective barrier provided thereonand not having said anodization layer provided thereon.
 19. The bellowsshield as recited in claim 1, wherein said protective barrier is notprovided on said inner surface and is not provided on any portion ofsaid interior surface.
 20. The bellows shield as recited in claim 19,wherein said inner surface and said first surface of the interiorsurface each include an anodization layer provided thereon; and whereinsaid mating surface is a bare metal surface not having said protectivebarrier provided thereon and not having said anodization layer providedthereon.
 21. The bellows shield as recited in claim 1, wherein saidprotective barrier is not provided on any portion of said inner receptorsurface.
 22. The bellows shield as recited in claim 1, wherein saidfirst exterior surface, said second exterior surface and said sidewallform a shoulder structure configured to receive a shield ring, whereinsaid exterior surface is a bare metal surface having said protectivebarrier in direct contact therewith.
 23. The bellows shield as recitedin claim 22, wherein said exterior surface further comprises: a roundedtransition region coupling said outer surface to said first exteriorsurface; a rounded transition region coupling said first exteriorsurface to said sidewall; and a rounded transition region coupling saidsidewall to said second exterior surface.
 24. The bellows shield asrecited in claim 1, wherein said end surface comprises: a first taperedtransition coupling said inner surface to said end surface; and a secondtapered transition coupling said outer surface to said end surface,wherein said protective barrier is provided on said first taperedsurface, provided on said end surface, provided on said second taperedsurface and provided on said outer surface.
 25. The bellows shield asrecited in claim 24, wherein each of said first tapered transition, saidend surface, said second tapered transition and said outer surface arebare surfaces not having an anodization layer thereon.
 26. The bellowsshield as recited in claim 1 wherein said protective barrier is a spraycoating.
 27. The bellows shield as recited in claim 26, wherein saidmating surface comprises: a first mating surface coupled to said innerradial surface; a second mating surface coupled to said first matingsurface and said first surface of the interior surface, said secondmating surface being axially recessed from said first mating surface andsaid first surface of the interior surface.
 28. The bellows shield asrecited in claim 1, wherein said inner radial surface does not have saidprotective barrier thereon.
 29. The bellows shield as recited in claim28, wherein said inner radial surface has an anodization layer providedthereon.
 30. The bellows shield as recited in claim 1, wherein each ofsaid end surface of the second end, said outer surface of thecylindrical wall and said exterior surface of the attachment flange is abare surface not having an anodization layer thereon.
 31. The bellowsshield of claim 1, wherein said protective barrier is a coating whichcomprises yttrium.
 32. The bellows shield of claim 1, wherein saidprotective barrier is a coating which comprises YF₃.
 33. The bellowsshield of claim 1, wherein said protective barrier is a coating whichcomprises dysprosium.
 34. The bellows shield of claim 1, wherein saidprotective barrier is a coating which comprises Dy₂O₃.
 35. The bellowsshield of claim 1, wherein said protective barrier is a coating whichcomprises an oxide of dysprosium.